This invention relates to automated reading of characters printed in magnetic ink, and more particularly to alphanumeric character detection by generating an X-Y array of signals from multi-element magnetic read heads spaced in relation to the direction of character movement with tracks of one head overlapping the tracks of another head. 2. Description of the Prior Art
Magnetic ink character recognition (MICR) systems are widely used for sensing information recorded on documents such as checks, credit card slips, and the like. Sensed information is converted into processable data form.
In one type of reader, a transport moves a document to be read containing alphanumeric characters imprinted in magnetic ink through a reading station. At this station, a device sensitive to the character being passed therethrough responds to the magnetized material. The response is in the form of an analog signal the waveform of which is unique to the particular character.
MICR readers employ a magnetic read head which generates an analog signal representing the first derivative of the magnetic field surrounding the character as a function of time. The analog signal is then processed by, for example, transforming the signal to a digitized output array. The data in this array is then compared with known signal arrays to identify the particular character read. A synchronizer or clock is utilized to interrupt the signal from the read head as a function of the space occupied by the character on the document. In this way, a discrete signal is generated which corresponds to a portion of magnetic field sensed during passage of a character over the head.
An improvement in MICR systems utilizes a multiple, linear array of read heads, one adjacent the other and placed perpendicular to the direction of movement of the character to be read. Such units read characters as a series of horizontal slices or tracks. The head reading on individual track responds to the magnetic field associated with the area of a given track. The response of each individual head may then be stored as a two-dimensional digitized signal matrix. By increasing the number of tracks, i.e., the number of heads, and by simultaneously decreasing the signal sample interval, the array may be expanded to provide higher resolution. Because of physical constraints, the total number of tracks into which a signal character may be subdivided is limited.
Despite this improvement, MICR systems still have significant shortcomings. Systems using known methods experience a reject rate of from about 3% to 7% of the documents. Rejects occur because of ink smudges, misalignment in printing of characters, improper ink densities and the like. The main problem is the dead space between elements in multi-element heads which misses signals centered between elements.